Spinal rods are often used for spinal fixation, including for correction of scoliotic curves. Fixation often involves implantation of rods by attaching them to the spine with anchors in the form of hooks and/or pedicle screws. Often, a pair of rods are placed on opposite sides of the spine.
Various systems have been developed for rigidly connecting two spinal rods together to prevent rod migration and to increase stiffness of the paired rod assembly. In many cases involving multi-level fusion of the spine, these systems stabilize the spine construct until solid bone fusion is accomplished. In the post-operative period before fusion occurs, a significant amount of motion can occur between the rods, wires and hooks, which can, for example, allow a scoliotic correlation to decrease or the pelvis to de-rotate toward its previous, deformed position. By providing a rigid transverse connection between two spinal rods, the loss of correction can be reduced and a stiffer construct can be created, which may enhance the promotion of solid fusion.
In some cases, the two side-by-side spinal rods that are to be interconnected by a rod to rod connector are not perfectly parallel to each other. In addition, the spinal rods may extend in different planes. Non-parallel rods that extend in different planes present a problem because many known rod connectors require the two spinal rods to be more or less parallel and co-planar. Many known rod to rod connectors cannot engage rods that extend in different planes. Longer rod pairs that span two or more levels can be especially difficult to interconnect, because the different planar orientations are more pronounced.